The overall objective of this research is to examine the interrelationships of both retinal and choroidal circulations using quantitative methods to measure blood flow in primates. The radioactive inert gas clearance method using Krypton 85 would be used to make quantitative measurements of choroidal blood flow and a fluorescein densitometric method would be used to make measurements of relative retinal blood flow. The former method gives values for choroidal blood flow in absolute units; i.e., mls, blood/100G tissue/minute, whereas the latter allows a quantitative estimate to be made of changes in retinal blood flow from a control situation. A second objective is to investigate and study choroidal filling patterns using cineangiography and to examine whether quantitative information could be obtained on macular and optic disc blood flow using infrared film and indocyanine green dye. This latter objective might provide a bridge between the inert gas clearance method which at present is unacceptable for clinical use, and a photographic method, which would give quantitative information on macular and optic disc flow in the clinical situation.